1. Field of the Invention
The present invention relates to an artificial limb joint device comprising body protecting members which adjoin to each other in a vertical direction and one of which can turn on an axial core in a direction perpendicular to the longitudinal direction with respect to the other body protecting member.
2. Description of the Related Art
There are generally known three different types of artificial limb joint devices shown in FIGS. 15A, B and C according to the prior art.
A first type of artificial limb joint device shown in FIG. 15A is manufactured by Fillauer Co. and makes it possible to adjust an angle between an upper body protecting member 50 and a lower body protecting member 51 continuously by interconnecting the upper body protecting member 50 and the lower body protecting member 51 by a pair of upper and lower plate-like joints 52, 53 and rotating a pair of vertical screws 55, 56 provided to a joint body 54.
A second type of artificial limb joint device shown in FIG. 15B is manufactured by USMC Co., and makes it possible to adjust an angle between an upper body protecting member 50 and a lower body protecting member 51 in increments of 5.degree. to 10.degree. by interconnecting the upper body protecting member 50 and the lower body protecting member 51 by a plate-like joint 57 and replacing a cam 58 for angle adjustment provided to the lower body protecting member 51 with another cam (available in seven types).
A third type of artificial limb joint device shown in FIG. 15C is manufactured by Becker Co., and makes it possible to adjust an angle between an upper body protecting member 50 and a lower body protecting member 51 in increments of 5.degree. to 10.degree. by interconnecting the upper body protecting member 50 and the lower body protecting member 51 by a pair of upper and lower joints 59, 60 and replacing a cam 62 for angle adjustment provided to a joint body 61 with another cam (available in seven types).
Although the first type of artificial limb joint device can eliminate the need, as in the second and third types, for replacing the cam 58 or 62 for angle adjustment and can adjust the angle continuously, it has such inconvenience that the adjustable range of the angle is narrow (about 5.degree.). Since the upper body protecting member 50 and the lower body protecting member 51 are interconnected by a joint, these artificial limb joint devices manufactured by the above three companies have at least two connectors: a connector between the upper body protecting member 50 and the joint and a connector between the lower body protecting member 51 and the joint. Therefore, the two connectors cannot absorb a torsion load received from the body during walking, for example. As a result, the joint is used to absorb the above torsion load efficiently. However, the joint is made from a metal in most cases. When the joint is made from a metal, it has poor flexibility and hence, prevents the natural motion of a man disadvantageously.
When the joint is made from a metal, it is excellent in strength but it is hardly returned to its original shape when it is deformed by a torsion load and may not be usable any longer. Therefore, as the joint must be constructed to be strong enough to withstand long-time use, the above inconvenience becomes marked and there is room for improvement.
When a man walks, one side of the pelvis first turns at 4.degree., the thighbone turns at 8.degree. relative to the pelvis, and the shinbone turns at 9.degree. relative to the thighbone. The total turning angle of the lower limb of these three segments is about 25.degree.. During walking, the inclination of the pelvis and hip, knee and ankle joints are used for bending and stretching. That is, the artificial limb joint device requires the knee joint and the ankle joint to turn at 9.degree. on a horizontal plane, and the shinbone turns when the repulsion force of the bottom of a foot against the floor is used to fix a foot portion. Therefore, it is ideal that the artificial limb joint device should have flexibility to absorb torsion and it is important that the artificial limb joint device should be returned to its original shape even when it is twisted.